Got my Barrett M82A1 with factory Swarovski Barrett scope off GunsAmerica, paid less than $7000 (August of 2005). The gun is damn near brand new. The caveat is I waited 2 years before I found one for the right price and shape, however, I was quite casual in my pursuit. If you are more diligent, you may find one sooner. They are out there, you just have to know where to look.
Remember...the 82A1 is not like buying a Glock pistol or S&W product. There are not many of them around, hence not many are for sale used. Mine was built in 2003, the serial number is in the 4000 range...and these things started production in 1985!
You are looking for the prized Rolls Royce of .50's, in my humble opinion. There aren't many out there to begin with, so be patient and one will turn up somewhere for the price and condition you want.
Patience, my dear boy, patience...